Erectile Dysfunction (ED, Impotence) (cont.)
Siamak N. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
In this Article
- Erectile dysfunction (impotence) facts
- What is erectile dysfunction?
- What is normal penis anatomy?
- How common is erectile dysfunction?
- How does erection occur?
- How is erection sustained?
- What are the risk factors for erectile dysfunction?
- What causes erectile dysfunction?
- How is erectile dysfunction diagnosed?
- What is the treatment for erectile dysfunction?
- What medications are used to treat erectile dysfunction?
- Oral phosphodiesterase type 5 (PDE5) inhibitors
- Sildenafil (Viagra)
- Vardenafil (Levitra)
- Tadalafil (Cialis)
- Avanafil (Stendra)
- Intracavernosal injections
- Intraurethral suppositories
- How effective is testosterone in treating erectile dysfunction?
- Can low testosterone level be replaced?
- Vacuum devices
- Surgery for erectile dysfunction
- What about psychological therapy for erectile dysfunction?
- What will research is being done for erectile dysfunction?
- Impotence (Erectile Dysfunction, ED) FAQs
- Find a local Urologist in your town
How common is erectile dysfunction?
Erectile dysfunction (ED, impotence) varies in severity; some men have a total inability to achieve an erection, others have an inconsistent ability to achieve an erection, and still others can sustain only brief erections. The variations in severity of erectile dysfunction make estimating its frequency difficult. Many men also are reluctant to discuss erectile dysfunction with their doctors due to embarrassment, and thus the condition is underdiagnosed. Nevertheless, experts have estimated that erectile dysfunction affects 30 million men in the United States.
While erectile dysfunction can occur at any age, it is uncommon among young men and more common in the elderly. By age 45, most men have experienced erectile dysfunction at least some of the time. According to the Massachusetts Male Aging Study, complete impotence increases from 5% among men 40 years of age to 15% among men 70 years and older. Population studies conducted in the Netherlands found that some degree of erectile dysfunction occurred in 20% of men between ages 50-54, and in 50% of men between ages 70-78. In 1999, the National Ambulatory Medical Care Survey counted 1,520,000 doctor-office visits for erectile dysfunction. Other studies have noted that approximately 35% of men 40-70 years of age suffer from moderate to severe ED, and an additional 15% may have milder forms.
How does erection occur?
Erection begins with sexual stimulation. Sexual stimulation can be tactile (for example, by touching the penis) or mental (for example, by having sexual fantasies). Sexual stimulation or sexual arousal generates electrical impulses along the nerves going to the penis and causes the nerves to release nitric oxide, which in turn increases the production of cyclic GMP (cGMP) in the smooth muscle cells of the corpora cavernosa. The cGMP causes the smooth muscles of the corpora cavernosa to relax and allow rapid blood flow into the penis. The incoming blood fills the corpora cavernosa, making the penis expand.
How is erection sustained?
The pressure from the expanding penis compresses the veins (blood vessels that drain the blood out of the penis) in the tunica albuginea, helping to trap the blood in the corpora cavernosa, thereby sustaining erection. Erection is reversed when cGMP levels in the corpora cavernosa fall, causing the smooth muscles of the corpora cavernosa to contract, stopping the inflow of blood and opening veins that drain blood away from the penis. The levels of the cGMP in the corpora cavernosa fall because it is destroyed by an enzyme called phosphodiesterase type 5 (PDE5).
What are the risk factors for erectile dysfunction?
The common risk factors for ED include the following:
- Advanced age
- Cardiovascular disease
- Diabetes mellitus
- High cholesterol
- Cigarette smoking
- Recreational drug use
- Depression or other psychiatric diseases
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